The present invention relates to an unbalanced twill weave fabric having variable strength between the warp and fill directions. More particularly, the present invention relates to an unbalanced twill weave fabric comprising fill yarns with a denier at least three times greater than the denier of the warp yarns. The present invention further relates to the use of such a fabric for occupant restraint devices and systems for increasing the safety of moving vehicles. In particular, one embodiment of the invention includes an inflatable airbag having a substantially tubular shape, wherein the airbag fabric is comprised of an unbalanced twill weave fabric.
Because of increased interest in automobile safety and passive restraint systems for the protection of the driver or passengers, inflatable airbag assemblies have become well known in the art. These inflatable airbag assemblies typically have a gas supply means and an airbag to which the gas is delivered. In the event of a collision, an impact sensing system activates the gas supply means which in turn inflates the airbag, thus providing a protective cushion for the vehicle""s occupants. The inflated airbag, acting as a cushion, prevents or reduces injuries to the vehicle""s occupants caused by violent contact with the inner surfaces of the vehicle.
Conventional airbag systems currently marketed, however, have undergone recent criticism due to injuries and fatalities caused by the airbag system itself. These conventional systems, which typically store an airbag in the dashboard or steering wheel of an automobile, activate the airbag in the direction of the automobile""s occupant. The force of the gases inflating the airbag has caused injuries to the occupants. Small children have been especially vulnerable to these types of injuries.
In response to these problems, it has been proposed to incorporate the inflatable airbag device into a seatbelt. Such an assembly, where the airbag is stored in at least the shoulder harness of the seatbelt, carries an advantage in that the airbag is stored in close proximity to the occupant. In the event of a collision, the airbag in the seatbelt activates from a position much closer to the occupant, thereby reducing both the forces generated by the airbag in the direction of the occupant and by the occupant""s forward motion in the direction of the airbag. Reduction of these forces may reduce the occurrence of injuries caused by the airbag""s impact against the vehicle""s occupant.
The design of such an airbag as part of a seatbelt assembly presents many challenges. Among these challenges, the airbag should have a relatively compact and lightweight structure for easy incorporation into or replacement of a typical seatbelt system. At the same time, however, the airbag must have the strength to withstand the forces of the inflating gases and the occupant""s forward motion. These criteria have stood in the way of practical and effective airbag-seatbelt systems.
It is therefore an object of the present invention to overcome the foregoing and other difficulties encountered in the prior art.
Another object of the present invention is to provide a fabric having particular qualities in terms of strength, weight, and thickness.
Another object of the present invention is to provide a fabric having greater strength in a particular direction of the fabric.
Another object of the invention is to provide an inflatable occupant restraint device that is less prone to failure due to the forces acting in one direction by contact with a vehicle""s occupant and in another direction by the inflator gases.
Another object of the present invention is to provide an inflatable occupant restraint device having a size and weight suitable for incorporation into a seatbelt structure.
To achieve the objects and in accordance with the invention, as embodied and broadly described herein, the invention relates to a woven fabric formed of warp yarns and fill yarns, wherein the fill yarns have a denier at least about three times larger than the denier of the warp yarns.
The invention also relates to an inflatable airbag device having an airbag formed of a woven fabric constructed of warp yarns and fill yarns, wherein the fill yarns have a denier at least about three times larger than the denier of the warp yarns.